It is commonplace to manufacture pushbuttons for automotive controls with symbols or legends by painting the pushbutton and selectively removing a patterned portion of the paint by a laser. The resulting product is called a "paint and laser pushbutton". Such a pushbutton is particularly desirable when the button is made of translucent material and the control panel is backlighted to light up the pattern.
When a control panel comprises a plastic trim plate with apertures and pushbuttons loaded into the apertures, there is generally little, if any, contact between the painted sides of the pushbuttons and the trim plate apertures. However for buttons loaded from the back side of the trim plate, a rear portion of the pushbutton is made larger than the button which protrudes through the aperture and defines a ledge surrounding the button which abuts the rear face of the trim plate. In the process of painting the pushbutton, often with more than one coat of paint, the ledge also becomes painted. Because the ledge is painted, there is a tendency for the pushbutton to adhere to the plastic trim plate. This is particularly significant when the part is exposed to high temperature and humidity, and is further exacerbated with contact time and preload forces. Most types of paints used to coat plastics for automotive interior application exhibit the tendency to stick.
The obvious solutions to the sticking problem are to mask the part to prevent painting of the ledge or the remove the paint after painting. Both of these solutions are difficult and expensive. The ledge itself is necessary to retain the pushbutton in the panel and to prevent light leakage around the pushbutton; thus removal or severe reduction of the ledge is not desirable. The preload force is necessary to prevent looseness and rattling of the pushbutton.